Filter



Apvril 26, 1938. E. PFLANZ FILTER Filed July l5, 1935 2 Sheets-Sheet lE. L. PFLANZ April 26, 193s.

FILTER Filed July l5, 1955 2 Sheets-Sheet 2 Patented Apr. 26, 1938Unirse STATES PA'r'izN'iv OFFICE 13 Claims.

This invention relates to filters and particularly to sand filterssuitable for use in the preparation of water for drinking purposes.

Such filters normally comprise a filter basin in which a bed of Asand issupported on a layer of graded gravel. The water to be filtered issupplied above the sand bed and is withdrawn by suitable-perforatedpipes located in the gravel bed.

WhenV the lter becomes fouled it must be washed and this washing isno-rmally effected by introducing water under pressure by the outletpipes, which water ascends upwardly through the sand bed, converting itinto an ebulliting mass of quicksand. The rapid movements of the sandparticles and their collisions have the effect of removing dirt from theparticles, which dirt is carried away by the wash water.

One effect of such washings is to subject the sand to repeated hydraulicgradation and the inevitable distribution of the iinest particles ofsand at or near the top surface. The result of this location of thefinest sand is that the top surface has a very effective ltering orstraining action and the lter becomes choked by a superficial skin ofdirt, the schmutzdecke, at a time when the ltering ability of the mainbodyY of sand is only slightly, if at aILimpaired.

Eiforts have been made to remove the nest sand, with the expectation ofavoiding excessive filtering at the surface. Such efforts have beenwithout success because fine sand is produced by attrition duringwashing and only a very small quantityV is necessary to ll in theinterstices between sand particles of normal size, resulting in somewhatexcessive filtration at the surface.

In my copending patent application Serial No. 708,179, filed January 25,1934, I have described and claimed a filter which is provided withperforated channelers which extend above and belowv the level of thesand surface. These channelers have the effect of providing a suitablygreater filtering surface, and also of providing a filtering surfacewhich is substantially devoid of the fine particles. .y

According to the present invention I .provideV means for producing inthesand an increased filteringfsurface, which is free and exposed directlyto the water to be filtered without .the interven- :tion of perforatedwalls or the like. This free surfacel of sand `is substantially freefrom the objectionable fine sand so that the free filtering Vsurfacesthus-provided have an enhanced filtering capacity',jpermitting.filtration to be exerted not merelyatfthe surface of the sand, but also(Cl. 21m-130) to a greater extent within the body of sand at somedistance lfrom the surface.

In the preferred form of my invention, `I provide an apparatus which maybe readily andV expeditiously installed in existing sand filters andwhich may be readily removed therefrom for theY purpose of repair andreplacement.

This apparatus will be fully understood from the following descriptionof preferred embodiments thereof, taken in conjunction with theaccompanying drawings, in which:

Figure l is a sectional elevation through aseries of filters embodyingmy invention;

Fig. 2 is a transverse sectional elevation, taken on the line 2--2 ofFig. 1;

Fig. 3 is a fragmentary sectional detail showing one of my sandsupporting elements on a larger scale, the intermediate portion beingbroken away;

Fig. 4 is a sectional fdetail view, taken on the line 4 4 of Fig. l, ona somewhat larger scale;

Fig. 5 is a view similar to Fig. 4, shcwing'the manner in which theksand supporting element Vis cleansed; f

Fig. 6 is a view similar to Fig. 4, showing a somewhat modified form Vofsand supporting element;

Fig. '7 is a fragmentary sectional detail view, Y taken on the line 1-1of Fig. 1, on a larger scale than Fig. 4;

Fig. Bis a similar view, taken on the same line as Fig. 4, and

Fig.Y 9 is a fragmentary sectional detail View, taken on the line 9-9ofFig. 8. Y

Referring to the drawings, the reference nu-A` meral l0 designates thefilter basin, which may suitably be of concrete. Adjacent one side,thebasin is provided with a wall ll which extends from the bottom of thebasin upwardly to a heightsubstantially below that of the side wallsofthe basin. The wall Il forms with the adjacent wall ofthe basin, achannel i2 for filter wash water. The channel l2 is drained bya pipe I3vprovided with a, suitablevalve (not shown). Be-

tween the wall ll and the opposite wall of the basin is located thefilter bed Mof sand which is supported by a bed of gravel 15,the YsizeVof which is graduated, the larger sizes being located at the bottom. Atthe bottom are locatedperforated draw-off pipes I6 which connect tomanifold l1, which conveythe filtered water away to suitable storagebasins (not shown).

Above the sand bed i4 are placed horizontal overiiow troughs lll whichare supported between the wall Il andthe opposite wall of the filterAbasin. These ytroughs are adapted to'nreceive Vwash water when the lteris being washed and convey it into vthe channel I2. y

The water to be filtered is supplied by the feed Vpipe I9 which isadapted to fill the basin in the manner indicated in Fig. 2. It will beunderstood 'Y that during ltering, the valve in the pipe I3 is closedand that the water passes through the Vsand bed I4, gravel bed I5v andperforated pipes I 6 into the manifold Il. l i n I provide in each lterbasin I3 a suitable-number of 'sand supporting elements 20 which willfnow be described. Each element 20 provides a support for sand sov as toestablish a channel in which areas or surfaces of free sand arepresented for the admission of water being ltered. For reasons. whichwill hereinafter Vbe more fully pointed out,rthese freeV areasorsurfaces are characterized by a substantial absence of ilne sandparticles which have the effect of accelerating the sealing of thefilter by schmutzdecke As will also be more fully explained, means arelprovided in each sand supporting element lso that thesame may besubjected to localized washing, whereupon filtering maybe continued. Inthis way the need for a general washing of the iilter 'can be postponedrepeatedly withpgreat economy of washing water.Y Y Y rMy. improved sandsupporting element comprises vertical series of plates laid obliquely.Two such series are located near each other with their plates divergingdownwardlyafter the manner of a herring-bone pattern. The upper 'ends ofthe plates of the two ser-ies are `in spaced relation so that a channelis formed which aids (in the formation of the free areas or surfaces ofsand referred to. lThe two seriesof plates eX- tend into the sand andthe spaces between adjacent plates of the same series are lled, for

Y.the most part, with sand. At the-'upper ends of between the two seriesof plates'. In this Way',

any impurities filtered out by the water, and alsol anyvfine sand, areelevated.and-automatically thrown away from the sand'lsupporting elementby the action of the upper louvers. VThese louvers effectively preventthe return of such dirt and .ne sand. When washwater is thus in-Vjected, the sand in and around the Vsand support- 1 ing elementisntransformed into .an ebulliting Vmass of quicksand, and themutualcollisionsfof the grainsY of sandfefiectivelyremove any adheringimpurities. When the rwater is shut off,

the dispersed sand within and around the louver plates settlesl downVvertically; but the lower edges of thelouver platesprevent'the' sand vonthe outside 'from iilling the spacesbetween the louver plates.V Thesespaces are available for the dispersed sand withinfthe louver platesandfthis Jsand settles within Vthese spaces, leaving a zig? zag 'channelfree of sand andv opento the sup-V erambient layer ofwater. n 5

y The sand'supportingelement shown comprises n -,a horizontal pipe 27|supportedon .brackets 22; l

4 and'23 carried'byfthe basin I0. One end4 of the pipe-2| lis closed.the .other end is kconnected to Y `a supply pipe 24fthrough which issupplied the waterfor the cleansing of-the sand supporting element.Pipes 25, in any suitable number, are secured in depending and equallyspaced relation from the pipe 2|. Each pipe 25 is threadedY into a boss26 in a bridge member 2'I which extends across the Vupper face of atrough member 28. At each end the trough member 28 is provided with aflange 29.*` The contiguous flanges 29 of the trough member 28 areconnected by bolts 30 so as to form a continuous trough along the lineof the sand supporting element. 'Ihe upper ends of the trough members 28are closed Y by means of perforated plates 3| which rest on `the upperedges of the sides of the trough mem- .f

ber and on the upper edges of intermediate webs 22. 'I'he intermediatewebs: 32 are provided with openings so that the water supplieddownwardly by the pipes 25 may be distributed uniformly within thetrough elements 28, from which it lescapes upwardly through theperforated plates ,The ends of the trough members 28 at theV extremeends of the sand supporting element 20, are closed by means of plates 33which extend upwardly beyondthe pipe 2| and are providedV with openingsthrough which that pipe passes.

A further vertical plate34 is located at each connectionbetweencontiguous trough members 28. j

The plates. 34 terminate somewhat belowV the pipe 2| and at theirlowerends they are provided with an opening 35, best shown in'Fig. 7,which conforms to the interior of thetrough members 28. Each p1ate`34carries'a flange'36 y `which conforms in shape Vto the vanges'Zil-'ofthe troughmembers 28.! This flange is interposed between adjacent-troughmembers 28Vdur- Y ing assembly and the bolts 30 pass therethrough.

.latter construction has the improved AVmerit of- 'causing a greatersupply of the-wash Ywater'to` enterinto the spaces betweeni-jvfadjacentlouvers;

The Yplates 33and 34 serve .as` supports for` the inclined or louverplates 3l'. These plates are in the form of slats which extend in thelongitudi- Y nal direction of the sand supporting element from one plate33 or 34 to the next.- The plates verse direction of the sand supportingelement from the vicinity of the longitudinal central vertical plane ofthe sand supporting element. As will readily be seen fromV Figs. 4to Y8,there are two series of such plates, one on each side of said centralplane.V The upper ends of the ,platesi31 of veach series. are in spacedrelation so that a` free passage is providedl in the upward direction,

as shown by the sinuous arrow 38 on Fig. 5. It

may here be noted that I do not inte-nd to be limited to'plates havingtheirlupper edges in the same vertical plane. since the location of theedges-otherwise does'not detract from thefdi's-V 3l slope downwardly andoutwardly in thel transf tinctive operation of this invention, providedthat Y the two seriesof plates 31 are reasonably near K each other. Inother words, the upper endsofV Vthe plates shown in Figs. 4 and 5 may beextended or reduced within wide limits without departing yfrom myinvention The series of plates or louvers 3l extend from a point nearthe trough elements 28 upwardly to, some distance above the normalsurface of the sand.

the embodimentshown in Fig. 6, the plates are progressivelyilonger, withthe rresult that vtheir i767* lower or outermost edges varelocated"onplanes-frA vIn the modicaton of the invention shown H1135y YFigs-4 and 5, the lower and outermost edges ofVv :1

fthe plates 31 are located inf'v'ertical planes; In f which divergeoutwardly and upwardly.V Y, This enbase The operationis as. follows: The,sandsupportingelements being installedin.the-,n'iannerl abovedescribed, the valves are. open 'to admit water from pipes Mintothetroughelements 28, This wash water vpasses upwardly through the sandcontained between. the adjacent louvers31 and also the adjacent. sand',as suggestedin Fig. 5, The incoming water transforms this sand intoA anebulliting mass ofquicksand and a'certainpart of the sand iscarriedupwardly. and dischargedlaterally between the uppermost louversowing. to theA increased volume ofquicksand over the com# pact 'sand'from which it' has been formed. It will be` noted thatthere is an.especially str ong current passing upwardly through thesinuous passage38` and that this st rongv current isparticularly adapted to carry .awayanyl fine and comminuted sand so that this sand is discharged on thesurface of the sand bed on either side of the sand supporting element.

When thelwater supply to the pipe 24 is turned off, vthe ebulliting massof sand settles by gravity into the state shownj in Fig. 4, That is,thesand which is located in the sinuouspassage 38 settles and compactsfor the most part into the spaces between adjacent louvers 31. 'Ihesandestablishes itself between adjacent louvers on its natural angle ofrepose and thus forms two series of free filtering surfaces, whicharedesignated 39 in Figs. 4 and 6. It will be notedv that there is` afree passage extending between the two series of louvers and open to thesuperambient layer of water. This passage extends nearly down to theWashing trough elements 28, but I have found that thesand lls upsufiiciently to prevent the formation of free surfaces between thelowermost and next lowermost louvers of each series.V ItY may be notedthat the water supplied by the pipe 2,1! need not be filtered water,but'rnay be part of the supply which is to be filtered. This arisesbecause this water has to pass through the` large thickness of the sandlayer beforev it can Ypossibly reach the pipes I6 and I1.

The filter is operated in substantially the same manner as anordinarysand filter. That is, the valve inthe pipe I3 is closed, thelter is supplied with water by the' pipe I9, and the valve in the pipeI1 is opened to permit the filtered waterto pass off. The waterpercolatesthrough the sand bed I4 .and owing to the presence of'theextremely finesand on the 'surface of the sand bed, the schmutzdecke l0vforms upon the surface of the'sand b ed'in arelatively short time. As iswell known to thoseskilled inthe art, this time depends upon'manyfactors and primarily depends uponthe season of the year and theresulting algae content of the water supply. The water also enters thesand vbed through the filtering surfaces 39. These surfacesvprovide agreatly increased filtering area for'the filter. Furthermore, as hasbeen pointed out above, they are substantially devoid'of very fine sandparticles. The resultis that the filtering is not conflnedto theksurface. 0f the sand to anything like the extent which prevails at thehorizontal surface of the sand bed. As a result, the surfaces 39 do notbecome sealed by schmutzdecke until a longer period of operation haselapsed. When, however, the filtering rate of the filter becomesexcessively low, a certain amount of water isv supplied by the pipe 24so as to convert the sand in and around the sand supporting element intothe ebulliting mass of quicksand previously described. lhetupwardpassageofthe wash water carries the dirt 'and'leaves` the 4surfaces39and thei .adjacent sand in l. condition forcon-v timed 'itiiatioii,y 1This Vpredlli` may bel 'conmld 0 I`. 1I1g time, for.,v example, untilthe. sand supportingzelei ments have beenwashedQve or six times. Then itbecomes necessary to apply a general washfto theI filter, whichfmaytbefdone in Vthensyual` manner, that, is, by opening the Yvalveinthe pipef I3'Y and supplying'filteredv water" under. pressure throughthe pipe I'l. vThis generalwash has v,the effect; ofthoroughly agitatingthe complete san'd bed. I4, and dirt.' vand scum, including vthe schmutz deckef is-fdelivered into theV troughs l'I8 from which it isdischarged into' the passageV I2 to the pipe I3.` After this' generalwashing, the sand sum'acrtingv elements 20 are subjected toa localizedwash., for the purpose of establishing the free surfaces 3 9,abov ereferred to. The basin Ill is .thenfllled with water and filtration isresumed.` .y i Although theinventionhas been disclosed in connectionwith" the specific 'details of preferred embodiments thereof, it must beunderstood that i Ysuch details are not intended to be limitative of theinvention'except in sofar as set forth in the accompanying claims, lHaving thus described my invention, what I claim a 'new and'desire tosecure by Letters f Patent of theUnited States is:

l. A filtercomprising a basin adapted to con'- tain liquid to beltere`da filtering bed of sand in the lowerparii of saidk basin,individually spaced members defining an open channel` extending fronithe space above the sand bed downf Vwardly into said bed and supportingsand therein with free surfaces exposed to said channel, and

' water supplying` means having a large effective water dischargingareav below and extending completely undersaid channel forming memberswhereby washing .water may be caused to pass between said membersintosaid channel to disturb and clean the'sand forming said freesurfaces. f Y

2. A filter comprising( a basin adapted to contain liquid tobe filtered,a' filtering bed of sand in the lower part of said basin, parallellouver V.elements in superimposed spaced relation defining achannelfextending.. from the space above the sand bedinto'the bed, saidlouver ,elements supporting sand with free surfaces exposed to said "inthe lower part of said basin, an adjacent pair of series of elements'-defining between them an* open channel extending from the space abovethe channel, and meanshbelow said louver elements v bed downwardly intosaid bed, said` elements supporting between them lsand with freeysui'ffaces exposed tojsaid channel, andineans below both s eriesfforsupplying water upwardly betweenv the elementsof each series into saidchannel." i

4. A filter comprising a basin adapted to contain liquid to be filtered,a filtering bed of sand in the lower part of said basin, a pair ofadjacent series of superimposed spaced louvers dening a channelextending from the'space above the bed downwardly into the bed, saidlouvers supporting sand with free surfaces exposed .to said channel, andmeans below both series for of each series into said channel.

supplying y'water 'upwardly between vthe louvers 5. A filter comprisinga basin adaptedrto con.- tain liquid to be filtered, a filtering bed ofsand in the lower part of saidk basin, and a pair of adjacent series ofsuperimposed louvers in lspaced relation defining a channel` extendingfrom the space above the bed downwardly into the bed, said Vlouverssupporting san-d Awith free surfaces ex-' posed to said channel, theupper endsV of the louvers of Vone series being Vin substantial verticalalignment with, and in alternating relation to the upper ends of theVotherseries, and said louvers diverging downwardly andoutwardly.

6. A filter comprising a basin adapted to'contain liquid to be filtered,a ltering bed ofr sand in the lower part of said basin, and a pair ofadjacent series of superimposed louvers in spaced relation dening azig-zag channel extending from the space above the bed downwardlyintothe bed, said louvers supporting sand with free vsurfacesexposed to saidchannel, the upper parts of the louvers extending into a vertical planeandthe louvers of one series being staggered relatively to the louversof the other seriesto provide said channel and said louvers divergingdownwardly and outwardly therefrom. K 7. A filter comprising a. basinadapted to contain liquid to beltered, a filtering bed of sand inthelower part of said basin, and a pair of adjacent series of superimposedlouvers in spaced relation defininga channel extending from` the spaceabove the -bed kdownwardly into the bed, said louvers supporting sandwith free surfaces exposed to said channel, the upper ends of thelouvers extending into a vertical plane and be- .ing located inspacedrelation to provide said channel, and said louvers divergingdownwardly and outwardly therefrom, saidv louvers lbeing progressivelylonger in the upward .direction Vof theseries.4 Y.

8. A filter comprisinga basin adapted to contain liquid to be filtered,a filtering bed of sand, a "series of louvers defining an open channelextendingy downwardly fromv the space above the bed into said bed andsupporting sand therein ,with yfree surfaces exposedto said channel, and

.of seriesof louversv defining between them an f openVv channelextending downwardly from the space above said bed Vintosaid bed,safid'elements supporting between them sand with free Y surfaces exposedto said channel, and water supply means located below each of saidseries of louvers adapted to supply water upwardlyv between the adjacentlouvers of eachseriesrto wash the sand contained/.therebetween andremove dirt and fine sand therefrom upwardly through said channel. y l Y10. A filter comprising a basin adapted to contain liquid to befiltered, a filtering bed of sand, a pair of adjacent series ofsuperimposed louvers in spaced relation defining a channel 'extendingfrom the space above the bed downwardly into the bed, said louverssupporting sand with free surfaces exposed to said, channel, and watervs'up-` ply means below each series of 'louvers adapted tosupplywaterupwardly between the adjacent louvers of each seriesrto wash thesand con-` tained therebetween and remove dirt andfine sand therefrom'upwardly throughsaid channel.

11. A filter comprising Aa basin adapted to .con-

' tain liquid to be filtered, 'a filtering bed of sand in thelowe'r partof said basin, a pair'of a'dja'fk centY series of superimposed louversVin spaced ree lation defining a lchannel extending from the space abovethe bed downwardly into the bed, I said louvers supporting sand withfree surfacesV 12. A lter comprising a basin adapted to contain liquidto be filtered, a filtering bed of vsand in the lowerV part of saidbasin, a pair of adjacent series of superimposed louvers in spacedrelation defining a zig-zag channel extending from thel space above thebed downwardly into the bed. said louvers supporting sand with freesurfaces exposed to said channel, the upper ends Aof the louvers of bothseries being substantially locatedin a common vertical plane'and inspaced relation to provide said channel, and said louvers divergingydownwardly and outwardly therefrom y and water supply means beloweaclisei'ies of louvers adapted to supply water upwardlyV between thelouvers to wash the sand `contained therebetween and remove dirt andfine sand therefrom upwardly throughsaid channel.

13. A filter comprisinga basin adapted to contain liquid to be iilteredafiltering bed of sand in the lower part of said basin, a pair ofadjacent series ofjsuperimposed louvers4 in vspaced relation defining a`channel extending from the space'above said bed downwardly into the bed,said louvers supporting sand with free surfaces vexposed to saidchannel, the upper ends of the Y louversof both seriesV extending atleast into a common vertical plane and being Vlocated inV spacedrelation to provide said channel, and said louvers diverging. downwardlyand outwardlyr therefromsaid louvers being progressively longer in theupward direction of the series, andl water supply means below eachseries of louvers adapted to supply water which washes tliesand con"tained between the louvers and removes dirt and fine sand therefrom.V 'f

ERNST L. PFLANZJ, f

